1. Field of the Invention
This invention relates to a novel color salt consisting of an anionic optical brightener component and basic color component and more particularly, it is concerned with a color salt having the characteristics of an optical brightener component and a color component.
2. Description of the Prior Art
Up to the present time, it has been proposed to make clearer the color tone of a coloring matter by introducing into the molecule thereof optical brightening groups to form covalent bonds (Kuroki et al "Kogyo Kagaku Zasshi" 67 (2) page 67-71 (1964) and Yamada et al "Yuki Gosei Kagaku Kyokaishi" 29 (12) page 37-44 (1971), but this method has the disadvantage that not only synthesis of such a coloring matter is difficult, but also the intrinsic characteristics of both the components tend to be offset each other, since the introduction of optical brightening groups results in shifting of the absorption maximum wavelength of the optical brightener or color molecule, and has an influence upon the optical brightening strength and color tone of the former and the color tone of the latter.
Salts of anionic dyes and cationic dyes are described in Japanese Patent Publication No. 7675/1970 and Japanese Patent Publication No. 15827/1970. However, these color salts show a color tone completely different from that of the original dye used for the production thereof, and it is difficult to estimate the color tone of a color salt to be formed and thus to obtain a color salt with a desired color tone.
In addition, Japanese Patent Publication No. 6312/1970 describes a method of coloring fibers of cellulose acetate using a color salt consisting of an anionic dye and a specified cationic compound, and Japanese Patent Publication Nos. 45808/1972 and 1996/1973 describes salts of anionic optical brighteners of stilbene type with guadinine and salts of anionic optical brighteners with organo nitrogen compounds containing at least one nitrogen atom capable of forming a salt with the anionic group of the anionic optical brightener. Japanese Patent Publication No. 19362/1967 describes complex compounds of basic dyes with complex acids such as molybdophosphoric acid and tungstophosphoric acid. However, no reports have been made as to color salts consisting of anionic optical brighteners and basic dyes and accordingly, nobody knows the properties of these color salts.